text:
Can the guard frequency be used by non-aircraft / general public?
I am part of an organisation which regularly flies high-powered rockets, and thus files a TFR when we do so prohibiting aircraft from the area where we launch these rockets up to 10,000 ft. This TFR is frequently violated, presumably unintentionally, requiring that we stop our current launches and wait for the aircraft to leave. However, there are sometimes situations where an aircraft sees the rockets and seemingly comes to investigate or remains within the airspace as they are oblivious.
Would someone on the ground with a handheld air band radio be allowed to communicate with these aircraft to warn them that they are violating a TFR? Would that be permissible on guard, or would there be a different, more appropriate frequency? I am not an aviator so I am not sure if I could read a VFR chart to determine if there is a local frequency.
A further scenario that I am curious about ground use of the guard frequency would be in the case of witnessing a plane crash, if per chance you had an air band radio would it be appropriate to radio the location of the crash to any listening controllers/aircraft, or is this prohibited?

Hi Goulash, welcome to Aviation.SE!  Is there a reason that your organization is able to file TFRs but not able to determine whether an appropriate radio frequency exists?  I'm not asking maliciously, I'm just surprised that the responsible party for the TFR wouldn't have or be able to determine that information already.

I have no idea, I'm not involved with the organisational side at all, I'm just involved in the rocketry side of it. I'm only asking this question out of personal curiosity, not for advice to give to the organisation. My curiosity comes from a tangential interest in aviation and radio communications. It's certainly possible someone within the organisation who is responsible for filing the TFRs already knows the answer to this question, but I don't know who to ask and I still figured here would be a good place to get some good insight about rules for non-aircraft use of aviation frequencies.

Fair enough, it's a good question and I'm interested to learn the answers as well!

Assuming this is for amateur rocket launch, for US/FAA these TFR are managed like described in JO 7400.2 section 31. A waiver is granted by FAA, it should contain instructions for preventing intrusions, possibly a live contact with ATC (31−2−7) or a specific frequency announced in the activation NOTAM (31−2−8). Have you seen this waiver or a NOTAM?

Related: Which FCC license do I need to operate an aviation radio on the ground?

In an emergency, anything can be acceptable. For example there was fairly recent incident at Paris CDG where a mix-up between ATC and a flight crew resulted in the crew thinking they were instructed to make a late change to a parallel runway during approach, and would have landed on a runway that was already occupied. A pilot who was waiting for takeoff clearance realized what was happening and explicitly impersonated ATC, using the tower frequency, to instruct the landing plane to go round. (And the instruction was complied with, averting an accident).

@alephzero I'm not quite sure I'd say they impersonated ATC. The easyJet crew first called the tower to report the situation, saying "Tower,  there is a traffic  landing 09R," and then realizing the urgency of the situation called for the go around themselves: "Go around 09R go around." That's less impersonation of ATC and more one pilot addressing the other aircraft directly.

@ZachLipton Yeah, agreed. I didn't take that as an attempt to impersonate ATC at all, but rather one crew communicating to another upon noticing about an urgent action they needed to take. Which is, of course, always acceptable on aviation frequencies. Same as when the United crew told Air Canada that they were lined up on a parallel taxiway at SFO seconds before they were about to touch down on it (and the line of airplanes sitting on it.)

@alephzero: "In an emergency, anything can be acceptable", right in general and it's good to mention it. However there is an exception: You may have been given a more suitable mean to act in case of emergency, In the case of TFR, if the FAA waiver contains a way to report / prevent intrusion and which is usable, then it must be used, this is why I asked the OP whether they read the waiver, before starting to create another way to act in case of emergency.

It would probably be a lot easier, (and more appropriate) to coordinate with ATC by phone when an aircraft enters the TFR.  After all, they control the airspace.  You are just borrowing it and have no real authority.

As a former FAA ATC'er, National Association of Rocketry high-power Level 3 certificate holder, and the facility approver guy for high-power rocketry waivers in our facility airspace, if you are in the USA, you do NOT have a temporary flight restriction (TFR) for your rocket launch, but instead you have an FAR waiver and a notice to airmen (NOTAM). This merely informs the public that launch activities are taking place. Pilots are not precluded from flying through the NOTAMed airspace, therefore they have not violated anything, and transmitting a violation would be wrong, in addition to the FCC issues already mentioned.

This seems like a credible answer, and presuming it is correct, highlights that @Goulash would be advised to ensure that they and other members of their rocketry club have a complete understanding of rights and responsibilities regarding deconfliction with GA.  Because presuming a TFR is in effect could very well be completely wrong!  (although it sounds like they are playing it safe...)

There are two high power rocket sanctioning bodies in the US: NAR (mentioned above) and Tripoli. Both organizations require that immediately prior to launch, the airspace is clear and will remain so during the launch/recovery. If you examine the airspace and see an aircraft coming, you don't launch. If an aircraft is loitering as mentioned by the OP, you wait until they are gone.

At least in the "jurisdiction" I'm somewhat familiar with, EASA and my country,  licences are required for both the radio device and the operator of the radio. The training required for personal licence is not that hard, consisting of legal stuff, theory and learning the standard phraseology for radiotelephony. Once the personal licence is acquired, one can apply for a device licence and then puchase one, or use one already belonging (and licenced) by the organization.
I see no reason why your organization could not acquire licences and devices to monitor the airspace and communicate intentions and issue warnings to nearby aircraft. I'm actually quite surprised you do not have means of communication with other users of the airspace...
Caveat: your local laws and regulations may differ from mine, but generally I see a need to ensure flight safety by your organization being licenced for use of airband radios.

"licences are required for both the radio device and the operator of the radio" This is no longer required for pilots in the U.S. (though, of course, they still need to get a radio operator license if they intend to fly outside of the U.S.) Pilots can (and frequently do) purchase handheld airband radios from all sorts of stores (online and otherwise) with no license requirement. I'm not sure about the legality of this for non-pilots, but I'd be a bit surprised if it's illegal since student pilots don't actually require any sort of license until they're ready to solo.

You should make that an answer regarding U.S.

Well, it doesn't technically answer the question, since I'm not actually sure (and don't have a source off-hand) about the requirements for non-pilots, which is what the question is asking about. I've followed the question, though, and if no one that already knows the answer answers it first, I'll look into it.

@reirab US pilots in US aircraft in US airspace are “licensed by rule”, meaning they don’t need an individual FCC license. Passengers (including students) can also use a radio under the supervision of someone licensed, including “by rule”.

@StephenS Someone on the ground with an air-band radio, not in an aircraft, can't claim to be licensed by rule.

Speaking from my Canadian experience: You require a radio operator's license to transmit on frequencies used in aviation. Getting a license involves passing a knowledge test, after which the license is good for life. The required knowledge to pass the test would probably answer all of your questions. As I recall, it was a pretty easy test to pass. Among other things, you would learn how to structure your messages to make your communications concise and effective.
"Guard" frequency should be for emergencies only. I would imagine that no-one will object to a bystander using the guard frequency to alert search and rescue to a genuine emergency, licensed or not, but I'm not sure intrusion into a restricted area qualifies as an emergency. Anyway, pilots generally don't monitor the guard frequency as a matter of routine, so you should not expect an intruder to receive a warning issued over it. In many places there are enroute frequencies which pilots should be monitoring when not in controlled airspace or in an area where a specific frequency has been assigned. Your best bet would be to issue your warning on one of them. In Canada, those frequencies are 126.7 and 122.8.
FWIW, and again from my Canadian perspective, licensing is required to operate any radio transmitter in Canada, with certain exemptions, such as low power devices... at least that's the way it used to be.

" pilots generally don't monitor the guard frequency as a matter of routine"  also there may well be NORDO traffic up there!

Pilots do no require any radio operator license to transmit on aviation frequencies in the U.S. This hasn't been a requirement in the U.S. for decades (presumably because all of the relevant radio knowledge is already covered in pilot training, so it's rather redundant for pilots.) It's completely legal for pilots to purchase and transmit with either handheld aviation radios or ones built into aircraft with no radio operator license here. I'm not sure about the legal situation of this for non-pilots, though.

@reirab In Spain, licensed boat captains do not require a separate radio operator license to transmit on maritime frequencies either... because the captain license already allows them to do so. Maybe it is the same for US pilots? They do not require a radio op license because their pilot license "includes" one?

@walen That's not the way it works in the United States. Pilots on board aircraft are allowed to transmit by virtue of the fact that they're on board aircraft, not by virtue of the fact that they have pilot's licenses. Getting a pilot's license doesn't grant any radio privileges.

@TerranSwett Nice to know, thanks.

@reirab I am speaking from my Canadian experience from about 20 years ago. At that time, a pre-requisite for obtaining a private pilot's license was a radio operator's license, so a sub-set of pilot training included preparation for a radio operator license test, and the radio operator license was issued independent of a pilot's license. Although you can fly NORDO, it is considered more the exception than the rule, hence the radio license requirement.

@AnthonyX Yeah, that used to be the case in the U.S., but the radio operator license is no longer required for pilots here. We are allowed to transmit on the aviation bands without any radio operator license within the U.S. U.S. pilots only need a radio operator license if they're going to fly into other countries that still require it (which the vast majority of non-commercial U.S. pilots never do.)

In response to this:

A further scenario that I am curious about ground use of the guard frequency would be in the case of witnessing a plane crash, if per chance you had an air band radio would it be appropriate to radio the location of the crash to any listening controllers/aircraft, or is this prohibited?

I am not a current pilot but I do hold several current FCC licenses and I am a current first responder. This is not legal advice but it comes from experience.
In the USA there are a great many laws that you may break in an emergency with impunity. The criterion is IDLH, Immediate Danger to Life and Health, and if it is such a situation, you may generally take any measures that you deem appropriate, as long as they do not cause more danger.
I have yet to witness any FCC regulation that prevents a reasonable and informative report of something like an airplane crash. This holds for any band. I have yet to witness anyone getting yelled at for making this sort of report, ever, anywhere. Understand that you may be asked to clear the channel after your report is received, but somewhere, someone will thank you for having made the report.
Use common sense. Don't call it in if you know it's already been called in. But also consider that very often dozens of people will drive past a flaming car wreck on the side of the road without calling it in.
If you get ordinary cell phone coverage where you are, you will probably get much better results by simply dialing 911. People in the aviation community tend to be strong communicators with lots of resources and emergency training, but we have a network of people who are even better at dealing with this exact situation. Many locations also have 311 service for less emergency-like situations. I have been forwarded from 311 to 911 in the past, they can do that, they are trained to know when they should and they will do so immediately if they should.

In the US, the Federal Communications Commission (FCC) makes the laws and enforces them for radio communications, not the FAA.  The laws are contained in 47 CFR § 87.
Section 87.18 says, "An aircraft station is licensed by rule and does not need an individual license issued by the FCC" (the sentence continues with information not relevant here).  So people in an airplane don't need a license to talk on an air band radio.  You however are not in an aircraft, so in order to use an air band radio, you would need an FCC license.
In order to get an license to use the FCC's "Aviation Services" (the legal use of radios on aviation bands in the US), you would need to know exactly what kind of station license you're applying for.  There are many different types of stations, which are all specified in detail.  See 47 CFR § 87.5 - Definitions.  I counted about 25 different types of station.  Here are some examples:

Aeronautical advisory station (unicom). An aeronautical station used
for advisory and civil defense communications primarily with private
aircraft stations.
Aeronautical enroute station. An aeronautical station which
communicates with aircraft stations in flight status or with other
aeronautical enroute stations.
Aeronautical multicom station. An aeronautical station used to provide
communications to conduct the activities being performed by, or
directed from, private aircraft.
Aeronautical search and rescue station. An aeronautical station for
communication with aircraft and other aeronautical search and rescue
stations pertaining to search and rescue activities with aircraft.

The way to apply for any of the Aviation Services licenses (besides the basic aircraft station license for which no license is required) is to register with the FCC's Universal Licensing System (ULS), and then file a license application electronically there, which will be the equivalent of the old Form 601.
If you were to witness a plane crash, your radio on the ground may have a difficult time talking to another station on the ground, because of obstacles between the two antennas.  Air traffic controllers might not welcome kibitzing "civilians" who aren't familiar with their procedures on their frequency.  Calling 911 (emergency services) on the phone would probably be more appropriate.


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What were the typical military training aircraft of the mid- to late-1930s in USA?
I am writing a novel that includes 1939 to present. I am interested in what pilots in training first used when they were entering flight school during the mid-late 1930s in USA. Can you advise me?

Welcome to aviation.SE! I added the word "military" to your question because you had added the USAF tag. If I'm wrong about that, then of course you can edit again to correct it. If you're new to the site, the [tour] might be helpful to see how things work.

If you are referring to the first training aircraft flown (Primary trainer) by a cadet in the US Army Air Corps or the US Navy, then you are looking for the Boeing-Stearman Model 75, called "The Stearman", Kaydet, or by the United States Navy (as the NS and N2S). The Stearman was introduced in 1934 and was the primary trainer until the late 40s.
It should be noted the there were other trainers still used throughout that period, by both the military branches and the private aviation schools that were sometimes contracted by them.
In addition this would have been the first of several trainers encountered by a cadet, once the Stearman was mastered a cadet could expect to move up to more advanced trainers.

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Which one of these flaps is used on take off and land?
I’m really confused about which one of these flaps is used on take off and land?
I didn’t even know there were different types, I thought that the top configuration was the only used one today?
Also, which flap would a big airliner (like A320 use please)?

Does this answer your question? Why and when to use flaps?. And this

Hi Sophit, they don’t sadly, those questions are more about how they work, mine is more related to their uses

I’m really confused about which one of these flaps is used

Before answering that question we have to understand why there are so many kind of flaps. The main difference among the flaps in your picture is their complexity and efficiency.
Regarding complexity, just compare the actuating mechanisms of a simple plain flap in respect to a double-slotted flap:

(Plain flap, source)

(Double-slotted flap, source)
A plain flap just need a couple of hinges to work, while a double-slotted flaps need several linkages, actuators and tracks to move. Complexity obviously implies also an higher price and more maintenance.
Regarding efficiency, said "$∆C_l$" the gain in lift coefficient that the flap needs to supply, an efficient flap generate less drag than an inefficient one:

(Polar comparison for different kinds of flaps, source)
Looking at the plot on the right, just say that for our approaching manoeuvre we need a $C_l$ of 2: following the plot we see that a plain flap generates a relevant drag coefficient of 0.1 while a slotted flap generates only 0.05 i.e. half of it. Looking instead at the plot on the left, you can see that a plain flap reach that $C_l$ of 2 at some 15° angle of attack, dangerously close to the stall region; a slotted flap reaches the same lift coefficient at some 5° with a good margin to stall.
Summarising, going from top to bottom, we encounter flaps with growing complexity but better efficiency: a plain flap is easy to manufacture, maintain and actuate than a double (or even triple) slotted flap. Anyway the latter is more efficient and possibly safer.

which flap would a big airliner (like A320 use please)?

Typically you'll find a plain flap on GA airplanes and a double-slotted flap on a jetliner.

Aren’t plane flaps used in airliners at all?

The first picture shows a slotted flap.

@Raketenolli: yep, corrected, thanks

Jet airliners almost exclusively use slotted Fowler flaps as trailing-edge high lift devices, most of them single- or double-slotted, some even triple-slotted.
For takeoff, these are only partially extended to minimize drag (see also How do flaps help an aircraft take off at a lower speed, yet cause drag at the same time?). E.g. on the Airbus A320, config 1+F and config 2 are valid takeoff configurations, and config 3 and FULL are used for landing (see here for details: A320 flap settings).
Some airliners are certified for a flaps up takeoff (e.g. Airbus A300 and A310), but this is pretty rare and requires very high takeoff speeds.
Airliners also have high lift devices on the leading edge of the wing. Most use slats, some also use Krueger Flaps.

Where could I see a plain flap being used? Could I see it on an airliner?

@FlightWatcher You'd see plain flaps on something like a small single engine prop plane.

There seems to be a misconception in the question. Different aircraft have different flap systems, which are those depicted. But it's not like an aircraft has all those types of flaps and chooses some of them for different things.
There is usually one system of flaps (in airliners two, really, between flaps and slats) that is used for everything. Different maneuvers require different settings.

The type of flap “used for landing” will depend on the aircraft being flown.  Basically you will use whichever type of flap is installed on the airplane.
You don’t have a choice inflight, airplanes are designed and built with a certain type of flap depending on their size and complexity as other excellent answers point out.
There’s just one flap handle with different positions, and you will likely use different settings for takeoff and landing, but that’s about the only choice you have.

NOTE: If the question is about design considerations by aircraft category or type vs actual “use” then please clarify with an edit.

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Can an individual land a personal helicopter used for personal use in their son's yard within a subdivision for pleasure?
Can a pilot legally land a private helicopter in a private subdivision?

Per the FAA, per local zoning regulations, or per the HOA?

Per any of those!!  Which one of those would apply to a neighborhood?  Why in the hell would a responsible person fly over a neighborhood and land in the back yard within the community?  It wasn't a medical emergency for any injury.  It is the grand parent of the kids who live there just for showing off to the grand kids!!

Well, my point is you may get a good answer yet regarding FAA regs, (I don't believe there are any federal restrictions on landing on private property even in a non-emergency because that question has come up here before in case you want to search...) but we don't even know if FAA regs apply because you haven't said where this is.   (My US-centric view just presumed.) Anyway, there are so many possible jurisdictions even besides the ones I mentioned in my comment that this will be tough to answer.  (state, county, city, etc.)

For example, check this one out:  https://aviation.stackexchange.com/questions/433/can-i-land-a-helicopter-anywhere?rq=1

Also related: https://aviation.stackexchange.com/a/38742/7532 and https://aviation.stackexchange.com/a/38740/7532 and https://aviation.stackexchange.com/a/38747/7532  The question isn't really a duplicate, but the answers are informative.

It certainly is helpful to know the question context. There's a big difference between "There's a thing I want to do and I'm trying to find out whether it's legal" versus "Somebody did something and I don't like it and how can that possibly be legal".

The regs in FAA and Canada are very similar. Anywhere a pilot chooses to land is deemed to be an "aerodrome" (a landing place, not a licensed airport) and as such isn't regulated federally. It all comes down to local land use laws, and your own insurance requirements. It's probable that some local entity, state, county, municipality, or HOA has rules about aerodromes.  If your locality is very libertarian and has nothing, then it

Please provide a location. At the very least, provide a country.

The regs in FAA and Canada are very similar. Anywhere a pilot chooses to land is deemed to be an "aerodrome" (any landing place deemed suitable by the pilot, whether a licensed airport or not) and as such, isn't regulated federally once you make contact with the surface (other than clearance with people and objects regs, which usually don't apply when you're in the process of taking off or landing).
It mostly comes down to local land use laws, and your own insurance requirements. It's probable that some local entity, state/province, county, municipality, or HOA has rules about aerodromes, and if you land somewhere and someone complains, eventually you'll get some sort of ticket in the mail, or the cops will pay a visit to your son's house.
If your locality is very libertarian and has nothing at all, technically you're good to go, but then it's a matter of relations with neighbours, and the terms of your helicopter's insurance policy with respect the use of unlicensed aerodromes.  Fixed wing aircraft, (especially rentals), are often restricted to licensed airports only by insurance requirements.
Helicopters, maybe not so much, but there may be some rider buried in the policy, with language limiting operations to landings outside "built up areas" (like a subdivision). So you may think you're fine, with no repercussions from a local law standpoint other than annoyed neighbours, but if that kind of language is there, your insurer has a get-out-of-jail-free-card if you make a hull or liability claim because you clipped a small tree with the tail rotor and dumped the thing on its side. So at minimum, you should check that if you care about your insurance.


text:
Are paramotors a good option for someone interested in flying, if so, what kind of regulations apply to them?
I am someone who wants to learn how to fly something, anything that I can ride in because it's just cool, are paramotors cheap and easy to use enough to get from novice to safe pilot in about a year or 2 and how much would it cost? Also what kinds of areas would I have to be in in order to fly it?

Welcome Ryan!  This is a pretty broad question, and mostly opinion based.  (what's your criteria for cheap and easy?)  As such it really isn't a good fit for this site.  I would suggest finding an on-line community of paramotor enthusiasts and getting involved with them.  P.S. if the goal is to move up to traditional fixed wing aircraft don't see them being a beneficial stepping stone.  Too different.  Probably a fun hobby though, I've never tried.

@MichaelHall Ok, I'll probably delete this question if you think I should, and I'll try and find a community similar to what you described.

I wouldn't be too hasty to delete it in case someone can offer something more.  It might be closed by voting though...

If you're in the US, paramotors have no license requirements, being treated as recreational vehicles, not aircraft. So you can do whatever you want, although you still have to respect air regulations once airborne, so at minimum you have to learn the "rules of the road".
The main thing is you are flying a wing that is "delicate" in terms of its rigidity, and with an extremely low wing loading, so the physical risks are related to the sensitivity to turbulence and gusts, your legs being the landing gear. Find the most highly rated paramotor school in your area, or travel to one of the top ones, and go get properly trained.
Properly trained, besides learning how to control the thing, is how to assess risk and having the discipline to follow the do's and don'ts. If you watch all the videos of guys flying in convective conditions, or low flying, you have to remember that you have a relatively unreliable 2 stroke motor pushing you along, that might quit at a bad time, and turbulence close to the ground can brake your legs and/or back by smacking you in. Then there's the 3 BIGGEST hazards in paramotoring down low, power lines, power lines, and power lines. And also a 4th one, power lines.
Did I mention power lines?
It's a bit like float flying.  Easy to learn to do. The hard part is staying out of trouble, and that takes a lot of mental discipline.


text:
Determining optimum area of parafoil, and then drag
I am designing a parafoil recovery system for a small payload of 300x100x500mm (2.4kg).
I have chosen an Aspect Ratio of 3, and from a NASA wind tunnel test report, the coefficient of lift and drag is 0.98 and 0.194 respectively. (L/D) is 5.05 and optimum angle of attack for the parafoil is 9degrees.
The parafoil should descend at a max vertical velocity of 7m/s.
I am struggling to work out what the optimum area of the parafoil should be for this.
I then need to workout the drag of the system and the flight path angle and velocity to model the trajectory.
Any help would be greatly appreciated!


text:
Do you need to know takeoff and landing distances for all airports or just departure/destination?
I know that calculating takeoff and landing distance data is required by 14 CFR 91.103 but it states "runway lengths at airports of intended use." So of course as part of my preflight action I calculate takeoff and landing distances for the airport I'm departing and arriving at.
Let's say I'm doing a local flight and decide to do some pattern work at a local nontowered airport. Am I legally required to have calculated takeoff and landing distance for that airport?
Also for my landing data my school taught me just to use the same data I use in calculating takeoff distance (e.g. pressure altitude and temperature) but should I be using forecasted data? I don't even know where to find temperature forecasts besides winds aloft and using standard lapse rate down to the surface.

"Intended use" is pretty clear. You need to know the runway length for every airport you intend to use. Short of an emergency or a mistake, you shouldn't be landing at any airport you don't intend to use, so effectively this means every airport.
The better you can predict the actual conditions, the better off you are. If the available landing distance may not be enough under certain weather conditions, you can decide on "go/no go" conditions beforehand. Perhaps the runway is suitable at 15°C with calm winds but not at 40°C with a 10 knot crosswind. If you aren't sure what the actual conditions will be, do your calculations with the values that give the longest takeoff and landing conditions.
The point isn't to estimate the distance exactly- it's to make sure you definitely have enough distance! So be liberal with "fudge factors," as long as they make the calculated distance longer. Many pilots add 50% to the calculation right off the bat as a safety margin.

There is a difference between takeoff and landing distance, and runway length.  You need to know both.
Suppose your plan is to launch from Romeo, Michigan, overfly Fair Haven, and then do some pattern work at Marine City.

Link to above chart at SkyVector
You do your takeoff and landing distance calculation for Romeo and discover that you need 2,800 feet to take off and land. Winds are from 220 at 10 knots. No problem, the runway at Romeo is plenty long enough. You blast off and head to Marine City.
Arriving over the field, you glance down and notice that the paved surface of runway 4-22 is 3,070 feet long, but there's a 295 foot displaced threshold on runway 22.  Now the available landing distance is less than what your airplane requires.  Can you still land?
Hmm.  What if you land on runway 04?  You'll have the full 3,070 feet available to you...but you'll be landing with a 10 knot tailwind.  Can you still land?

Obviously I've chosen these airports on purpose to illustrate the problem. Most of the time, if you can take off and land at your home airport, you can take off and land at nearby outlying airports using the same data - but not all of the time.  You need to be aware of both how much runway your aircraft needs at a particular place, and how much runway you have at that place, before attempting a takeoff or a landing.
Otherwise, you're just crossing your fingers and hoping.


text:
Is it common for ATC to issue traffic advisories in relation to an "intersection" during VFR flight following?
I'm a student pilot working on my PPL and I just did my first solo cross country earlier today. While I was on flight following I received a call from approach that sounded like "N123 traffic 4 miles north of the ____ intersection indicating 1000 maintain VFR". I just read back "Maintain VFR N123" as I was a little bit lost on what they were talking about. After some research I now kinda know what intersections are but I had literally never heard of them and in my case it wasn't plotted by name on a sectional. What exactly do I do in this situation? Do I just tell the controller I don't know where that intersection is? Is it common to receive traffic advisories relative to intersections?

Were you already on FF or had you just been issued a squawk code? I ask because it's weird to throw a "maintain VFR" into a traffic call. When informing a pilot of their radar ID status, ATC will reference a navaid or waypoint or airport.

I always thought that telling an aircraft receiving VFR F/F, "Maintain VFR" was like telling the aircraft to, "Comply with the FARs." Totally redundant.

@RetiredATC, I completely agree. But a lot of controllers do it. And a lot of controller will also respond "maintain VFR" when a pilot reports traffic in sight. I've never before heard of a preemptive "maintain VFR."

@randomhead I always interpreted "maintain VFR" as a positive confirmation that "I'm not assigning a specific altitude or heading, thus you're free to maneuver as needed to stay out of clouds and at appropriate VFR altitudes." It's the alternative to "maintain [VFR at or below] 3,000" and/or "fly heading 120." So I don't see it as redundant. As an ATC, is that not your take on it, or do you have more insight? Thanks!

I also agree with the other comments that this sounds a lot more like a radar identification than a traffic pointout. Is the OP positive this was for traffic?

@TypeIA, the phraseology "maintain VFR" is mentioned in only three scenarios in the 7110.65: a VFR pilot requesting IFR clearance but unable to provide their own terrain/obstruction sep to the MIA; a VFR pilot requesting a practice approach; and an IFR aircraft executing an approach which will terminate in VFR pattern work. Any use by ATC outside of those specific scenarios is redundant and unnecessary. Technically it isn't even required that we say "maintain VFR at or below 3000;" if you're VFR, the instruction "maintain at or below 3000" or even "maintain 3000" does not make you IFR.

@TypeIA Late on this but I listened to this LiveATC archive and I completely incorrectly heard they were calling my location after establishing radar contact. Still they used an IFR intersection which is strange

Every time when something in communications is not known to you as a student pilot you should admit it and report to the ATC, especially when it is a time pressured nature.
Most likely what happened in your case is that air traffic controller simple "forgot" that you are VFR flight (controllers are humans too).
I always tell my students to advise controllers that you are a student pilot, for example on the solo cross-country. Although not 100% but most of the time you'll be treated with "extra care". You need to do it only in the beginning of the flight because when you switch controller handover will already have "student pilot" in the comments.
As the previous poster suggested the best was to say that you do not know where the waypoint is located and ask to clarify the location of traffic.

Welcome to Av.SE - great advice for students & no-longer-students as well!


text:
When provided with a taxi clearance do you need to immediately comply or can you take your time?
I'm a student pilot and I'm just wondering on if I receive a taxi clearance at an airport then read it back can I wait a minute or two before I actually start taxiing or do I start to go immediately? For example, let's say I'm on the ramp and call ground to taxi to the active for a southwest departure. I know I'll be expecting runway 23 since I'm familiar with my airport and have already obtained the ATIS and planned my expected route ahead of time. However, instead they tell me to taxi to runway 27L at Romeo via Foxtrot, Alpha, Romeo and then I read it back. If I'm unfamiliar with the taxi route can I take a second to check my airport diagram and make sure I know where I'm going as well as brief the updated route?

You are expected to comply when you receive clearance from ATC, and you are supposed to follow the exact taxi instructions.

This adds nothing to, and basically only restates, the existing answer. Please do not post further "answers" like this.


text:
What were the main differences between Whittle's British turbojet and Von Ohain's German one?
I cannot fully understand in simple words the differences between the axial flow engine (Von Ohain) and Whittle's centrifugal turbojet.

According to Wikipedia it was the other way around, Von Ohain centrifugal and Whittle axial

The centrifugal flow engine sucks air in the center of an impeller and flings it out by centrifugal force as it spins. The energy added to the air by flinging it out compresses it, and the compressed air is passed along to the burner cans. If you've ever seen the impeller of a vacuum cleaner or a water pump, it's pretty much the same thing, except the impeller is being spun by an electric motor instead of a turbine, and instead of a burner can, you have the vacuum bag or water tank.
An axial flow engine's compressor is more like a series of propellers with a shroud around them. It's a large number of spinning wings driving air straight back, like a ducted fan. You could think of the shrouded fan on your computer case as a single stage axial compressor (driven by an electric motor). Put ten of those fans in a stack, with each one boosting the air sent to it by the one ahead of it, with the air passage getting smaller and smaller as you go, and you have a multi-stage axial compressor.
So in a nutshell, a centrifugal compressor forces air to the perimeter of the compressor housing by spinning, then redirecting the air to the burner. The need to fling air at 90 degrees to its original flow path makes the engine quite fat. However the centrifugal flinging action makes the compressor relatively insensitive to flow disturbances or restrictions.
The axial compressor just drives the air straight back to the burner can down a narrowing passage with smaller and smaller sets of "propeller" blades. A much skinnier configuration, and a lot more efficient at compressing the air because you can incorporate many stages easily (you can make multiple stages with a radial compressor, but you have to stack the impellers and it's not desirable to do more than two at most), but since the axial compressor is basically spinning wings driving the air straight back, much more sensitive to flow disruptions, because they are wings that can stall like regular airplane wings.
Crude fuel control systems on these 1st generation engines being little more than a faucet operated by the throttle admitting fuel to the burner can, the Whittle engine was somewhat easier to manage by the pilot thanks to its relatively insensitive centrifugal compressor. The axial engines, while making more thrust with a smaller frontal area, were much more temperamental had to be very carefully monitored and managed when making power changes.

There are more instances where axial and radial were confused. 2. The Ohain engines also used radial compressors; you describe the difference between Whittle/Ohain (Heinkel) designs on one hand and Franz (Junkers)/ Oestrich (Bramo-BMW) designs on the other hand.

@PeterKämpf I believe the question already contains this misconception. Von Ohains first engine was a radial turbojet engine...


text:
Is it legal to take off from the road?
Specifically, I'm referring to the takeoff attempt which led to this crash (video here). This took place on highway 124 in Winnie, TX. Apparently the aircraft had just finished serving as a float in a local parade, and the pilot opted to fly, rather than be towed, back to the airport.
Incredibly, there don't seem to have been any injuries.
In the video, you can see that the police have stopped traffic, but this article suggests the local authorities were not involved.
My question is, is this legal? From an FAA regulation standpoint, in particular, but if anyone knows the laws for this area of Texas, I'm interested in that as well. Are there any regulations concerning what a pilot can use for an impromptu runway, and what sort of (obstacle) clearances need to be observed? What sort of permissions does he need to use a public road?

Guy missed a successful take off by about a foot.

A tiny bit of right rudder would have kept them clear, but it was still not great judgement.

In Germany (OK. it's not the USA) it would be forbidden: With exception of rescue aircraft (such as rescue helecopters) you need a permission of the LBA (the German counterpart of the FAA) to take off from any ground outside an airport. You would definitely not get a permission for taking off from a public road. And you would also not get a permission if there are obstacles next to the "runway" (as in the video you have linked).

Vehicles that use the public roads have to be road legal in the first place, don't they? At least in Europe, airworthy != road legal.

Jeez. how did clipping the light pole (apparently with the tip of one of the left wings?) cause the plane to lose altitude and crash?  Seems he could have just kept on going --  "The plane can be seen clipping a streetlight and then appears to strike cables holding traffic signal lights"  Oh.  Oopsie!

For this specific case, Texas laws prohibit overall the use of public roads for takeoff, still a municipality may issue an ordinance to allow some takeoffs from county roads, describing the specific procedure to be used.
The question boils down to whether such specific ordinance exists for this takeoff. A quick search on for the aircraft tail number and Chambers county ordinances doesn't return anything as of today. It's an offense unless specifically authorized, though the penalty, a fine between \$25 and \$200, doesn't seem to be a real deterrent.

FAA doesn't regulate off-airport operations

FAA requires a minimal safety height over terrain but indeed this doesn't apply for takeoff and landing.

FAA doesn't regulate off-airport landings/takeoffs, but pilots mustn't be careless or reckless.

Private helipad in Oregon, source. Go there with Google Maps
Other entities can regulate or prohibit off-airport operations

The insurance may prohibit operations off-airport.

The State may prohibit the use of public land for specific activities, including for air operations.

Air operations may be prohibited for purposes of noise protection, natural world protection, etc, so that one's hobby doesn't prevent safety, peace and quite for others.

Whether taking off from a highway is allowed depends on the State.
Texas and some other States prohibit off-airport operations
Texas specifically prohibits using public roads for takeoff and landing for any flying object, manned or not:

A person commits an offense if the person takes off, lands, or maneuvers an aircraft, whether heavier or lighter than air, on a public highway, road, or street except [...]

Emergency-related landings are indeed never punished and are possible everywhere, and it is conceivable some takeoffs may be emergencies too, but likely not in the present case.

Emergency landing in Texas on Interstate 35, source
Other exceptions must be specifically allowed by a local law maker (commissioners court of a county) using an ordinance:

A commissioners court of a county may enact ordinances to ensure the safe use of county roads by aircraft. An ordinance may:

(1) limit the kinds of aircraft that may use the roads;
(2) establish the procedure that a pilot shall follow before using a road, including requiring the pilot to furnish persons with flags at both ends of the road to be used; or
(3) establish other requirements considered necessary for the safe use of the roads by aircraft.

It's possible the operation you saw had been allowed by such local ordinance.
Some States allow them by default
In contrast Montana allows landings and takeoffs in general, though they are still subject to a procedure:

Aircraft landings and takeoffs from public roads in this state are lawful if proper safety precautions, as approved by the governing jurisdiction of the roads, are taken prior to the landing or takeoff

Fields, Oregon, source. How to get there, including the road landing on Youtube

Of course using a private property is not allowed without prior consent of the owner in addition of regulations mentioned above.
More: Is It Legal To Land A Plane On A Road?

A fine between $25 and $200?  Is that cheaper than taking off from an airport?

@AdamBarnes All but the largest airports in the US are free to use. Some FBOs charge a handling fee, but it’s usually waived if you buy gas or other services from them.

I feel like when you do a botched takeoff like this where you destroy a pair of traffic lights and utterly wreck your plane, it's going to cost A LOT more than 200 USD.

What is the relevant definition of a "Public Road" though - if the road has been specifically closed by law-enforcement, does that make it okay?  I ask that, because (in the UK) road-racing is specifically illegal, but only on open roads - temporarily close them officially and it is fine.

@MikeBrockington Generally speaking, a public road is any road that is on public land, which is any land that has not been patented. Notably, govt entities can own non-public land, and that does not automatically make said land public.

@StephenS  I understand perfectly well what a Public Road is "Generally speaking" - my question was rather specific, and also relevant to the details from the OP, since Law Enforcement may have turned an 'open road' into a 'closed road'.

@MikeBrockington: A public road where traffic would be stopped for the purpose of a takeoff would still be a public road. Whether law enforcement officers (in contrast with county court commissioners) can allow forbidden acts is another question. I'd say likely, but they bear/share the responsibility of the consequences, like when they allow someone to drive in a one-way street because of a jam, and there is a collision with a car coming from opposite direction.

RE "Texas specifically prohibit using public roads for takeoff for any flying object, manned or not:"-- would Texas consider a small lightweight radio-controlled model airplane to be an "aircraft"?  Is there any precedent on this?  Your statement seems to imply that such a thing would be prohibited from taking off or landing on public roads but I wonder if that position is really supportable.  And what about a frisbee?

@quietflyer: Obviously I don't know more than the law says, and replacing "aircraft" by "flying object" is not correct. To answer your question, I imagine Texas has no own definition of aircraft and relies on FAA one: "Aircraft means a device that is used or intended to be used for flight in the air." Whether models or frisbees are included there is not clear. I'd tend to say yes a tort lawyer may use this against a frisbee user who killed someone.

And since the FAA is currently using the term "Small Unmanned Aircraft System" to describe model airplanes, drones, etc... from the FAA's viewpoint a model airplane is obviously an aircraft-- but, legally speaking, I don't know that whatever crazy wonky definitions the FAA decides to dream up, really have any legal impact on the interpretation of Texas laws --

@quietflyer: Aircraft definition for Texas seems to be: "a device that is invented, used, or designated for air navigation or flight, other than a parachute or other device used primarily as safety equipment", so that would definitely include models and likely frisbees.

The FAA does not regulate where aircraft can take off and land. If you want a permanent airport or heliport they have requirements for safe approaches and landings, but only so it can be listed as a facility.
States and local authorities make laws where aircraft can takeoff and land. In Alaska use of roads is common, with appropriate consideration of traffic.

Indeed. I remember seeing signs on the parks highway cautioning cars to watch for aircraft entering the highway. Even as a pilot, that's not a sign I'm accustomed to seeing on a highway. - haha

beautiful picture. Looks almost idyllic.

@lurscher As what life might be like before somebody complained about everything. I like the pic at the beginning of the video which shows the pilot parked at the gas pump getting a fill up.

As far as the FAA is concerned, you can take off from wherever you like. Otherwise seaplanes and helicopters wouldn't be terribly useful.
Local laws vary concerning public roads.

There is a related case in Spain, a man with an Ultralight Autogyro run on the road towards a Gas Station to buy gasoline. He got a fine, even if the road was a common road, not a highway, where vehicles must be able to run faster than 60 km/h, and the machine run on its small wheels never faster than 20 km/ h.
Mopeds, agriculture vehicles are allowed running slowly.
The Spanish State is money-avid, and its personnel suffers a hard craving for having chances of applying sanctions, punishments. Blessings +

What was the motivation of the fine? We can imagine many reasons, including the lack of driving license or license plate, or driving under influence, or non valid insurance (I'd tend to bet on this one)

No idea https://youtu.be/nErz9ugCmLA indicates just police action.
btw: before 'Autogyro', ad of parts seller: 'AutoHero', sound same in Spanish
La Guardia Cerril de Alicante unidad PEGASO denunció 2 infracciones de tráfico, 1 de seguridad aérea, al piloto de autogiro, español, 38 años, circuló en carretera para repostar.
Agentes del PEGASO (Policía Especialista en Gestión Aeronáutica y de Seguridad Operacional) Alicante, identificaron y propusieron sanción a un piloto de autogiro, circuló varios km por carretera.
2 de septiembre 2021, carretera CV 815 Castalla (Alicante)
Blessings +

Mopeds don't need a driver's license, but it is conceivable that an open propeller is too dangerous to be allowed in road. Salut +


text:
Is diying a strong jet engine possible wih basic tools
Is it possible to manufacture a jet engine that provides 500 newtons of thrust with relatively primitive tools like a lathe or so , if someone did something similar can you provide me with the knowledge you obtained please.

This is off topic here. Engineering subject, rather. But no, it's not possible.

You could do it with a CNC mill to make a centrifugal compressor and turbine, housing etc. Or with really basic tools, just get a turbocharger and build the burner cans to join the compressor side and turbine side together. Lot's of ppl have built little engines out of automotive turbos.

This would require far, far more than just a lathe.  You'll have to do 3D milling of some fairly exotic materials to create turbines, sophisticated spin balancing tools, etc.
There's a DIY guy on youtube that will provide some insights on what's involved:
Warped Perception
Also, I highly recommend AgentJayZ if you have an interest in a deeper dive into all things jet engine.  He does not work on DIY engines, he overhauls/refurbs industrial and aircraft jet engines, but his videos can provide deep insights into how turbojets actually work.
AgentJayZ

The manufacturing state of the art and the best engineers available in the early 1940's were only barely able to make functional jet engines. Even with the knowledge on the internet available now, I doubt that the tools in most DIY shops can improve on what the best in the world were doing then.

To take the heat and huge rotational stresses, most of the engine has to be manufactured from superalloys which have been subject to exotic process treatments to maximize their strength. Those process steps are completely beyond the capabilities of any garage shop.
They are also enormously difficult to machine to the super high tolerances required in modern, high-powered jet engines that must last tens of thousands of hours at full power without failure.


text:
What is this Slot for in My Flights Overhead Panel?
Does anybody know what this slot is for in my planes overhead panel? I think it was an airbus A320 or similar if that helps. Opening it revealed what looked like a a black socket, but not for electrical plugs.

Thanks in advance,
James

No picture of the black socket? That would be helpful. Can you describe it in more detail

Yes it did, that kind of circle but all black and possibly plastic. It had the smaller hole in the middle too.


text:
Does SkyVector's flight plan give wrong magnetic variation corrections?
Lately I have noticed that Skyvector's Flight Planning tool "Nav Log" has been showing very wrong magnetic variation corrections for particular legs of my flight plans. The corrections appear to be egregiously wrong and this has been going for at least a few months (since I've noticed). That combination makes me doubt myself, since I'd imagine it would be fixed by now.
I created an example route to show what I mean. I made the route KFRR to KLVL which goes along the 10W variation line:

I included some waypoints on the way to see when Skyvector would give bogus magnetic variations. And sure enough this is the flight plan it reports:

I highlighted in red the legs where it gives a +6 variation correction instead of what should be the correct +10. Is this just simply a bug or am I missing something here?


text:
What are the current challenges in software engineering for avionics?
I'm a software engineer working outside the aviation field, but I'm really passionate about avionics and I'd like to do my Master thesis in the area of software engineering for avionics.
Unfortunately, I lack the avionics background in order to know which are the key challenges in this field. I would to like to ask if someone can share some insights on it or maybe share some references for this topic.
Thank you!

I'm voting to close this as it's clearly asking for opinions.

Describing the issues and solutions in a field of engineering has nothing to do with opinions. Can we please be reasonable here on this site. Voting to re-open.

@ymb1 The question drew four upvoted answers, are they unsuited for this platform as well?

The question was closed because it was deemed to be asking for opinions. There is now a new reason launched to keep it closed: lack of research. Does that mean that this question will be closed as well?

@ymb1 well, I looked in the help centre, and aircraft design and manufacure is on topic.

Let us continue this discussion in chat.

As others have mentioned there are a lot of aviation specific aspects to the avionics software development process. The majority of these fall into two main categories; functional and certification.
Functionally, it has to perform its intended function reliably and safely. To do that it has to be developed to a Design Assurance Level (DAL) commensurate with the criticality of the software function. Process standards exist that all companies follow when creating their internal processes.
The key standards are:

DO-178C, Software Considerations in Airborne Systems and Equipment
Certification
ARP4754A, Guidelines For Development Of Civil Aircraft and
Systems
ARP4761, Guidelines and Methods for Conducting the Safety Assessment
Process on Civil Airborne Systems and
Equipment

And there is the actual function of the software and the realities of the aviation market. Most of the software is real-time embedded code and has unique interfaces to various hardware. And then there's the fact that the average life of an aircraft is 20 years or more and it requires ongoing support.
The second part, certification boils down to demonstrating to the certification authority that your software meets all the requirements and is safe. That boils down to primarily requirements traceability, testing, and documentation.
That's all challenging work, but while it has evolved over the years, the process hasn't really changed that much in the last 25-30 years. Avionics companies know how to do this and new hires learn the process when the come on board. What has changed is the tools and the hardware platforms and the expectations of the aircraft manufacturer's.
One of the biggest challenges is dealing with hardware obsolescence. The lifecycle of many processors is a few years at best. And as they've become more complex, there are resulting questions about the DAL of the hardware which resulted in RTCA DO-254 / EUROCAE ED-80, Design Assurance Guidance for Airborne Electronic Hardware, the hardware equivalent of DO-178C. The issue is that most processor manufacturers have no interest in any of this as aviation is a trivial percentage of their market. So avionics designers resort to multiple dissimilar processors with crosschecking, which adds more overhead and complexity to the software. Some have started designing their own processors to address the DAL, but even that doesn't solve the lifecycle issue as they typically rely on an external chip fab and the technology changes cause the fab to declare the process obsolete.
So what are the real current challenges? The aircraft manufacturers want lower SWaP-C -- Size, Weight, and Power, and Cost. The first three are hardware. That's being addressed by increased integration and Integrated Modular Avionics (IMA). That, in turn, affects the software as now your software has to run hardware that you don't control. You get to develop it on a development platform and then integrate it onto the aircraft. Ref: DO-297, Integrated Modular Avionics (IMA) Development Guidance and Certification Considerations. And if you want to sell it to more than one manufacturer, it may have to run on different hardware. The key to most of these is the IMA platform operating system which allows the functional software to be (mostly) hardware agnostic.
The last 5 years or so, the major challenge to avionics software has been to reduce cost. Not just the cost of development, but the cost of integration and the cost of changing the software in the future. When the manufacturer askes for a new feature and you add it to the software, you have to flow through that process all over again. That can get expensive real quick. To reduce cost it takes a well designed software architecture that allows for modular design and testing capabilities at the module boundaries to limit the impact of change.

I don't have experience with avionics, but I do have some experience with medical and the principles are similar.
In my not very humble opinion, the main challenges are paperwork, paperwork and more paperwork and having to live with technology that is either 30 years old or total usability horror, because it is not objectively safer, but happens to have the paperwork done for it.
For safety critical systems, of any kind, not just software, it is required that risk analysis is done and the system must be designed and implemented so that qualified estimate of mean time between critical failures (= failures that result in an accident) is lower than some value. For systems that can kill multiple people the requirement is usually 10⁹ hours.
That estimate involves all kinds of failures, both software and hardware, and across all parts of the system. The components (both software and hardware) are tested to get some basic reliability for them, and then checks and backups have to be provided so that any particular type of fault, which is almost always more likely than once per 10⁹ hours, won't result in an accident, and the combined probability of enough faults to cause one at once is below the desired threshold.
Now for software that means that it has to be comprehensively tested, which is fine. But it is also required that the tools involved in building it are “validated”. The stated purpose is that you know what is the risk of fault in the tool creating an undetected fault in the product, which is needed for the overall risk analysis. However:

The way I've seen it done in practice usually missed the point completely. Some requirements were created and then the tool tested to show it satisfies them. This was a lot of work, but the requirements defining what the tool is supposed to do—e.g. for a compile the specification of the language—didn't really tell anything about either risk of the tool introducing a bug—e.g. compiler producing functionally different code in debug and release mode—nor the risk of it becoming critical—if you test what you fly and fly what you test, you don't create any different builds that could have a difference.

Due to the amount of work involved it means you are often stuck with a special compiler that only supports old standard (like C89), has a lot of known limitations and comes with its own terrible, ugly IDE, only because the vendor did the validation for it while the general tools like gcc or clang don't have it. Now take into account that the validation only really makes sense in context of the specific project, so all that paperwork may not really improve the reliability of the product, just serves as an important liability shield for the company.

Fortunately the code itself tends to be fairly simple. Anything that should be real-time, i.e. have guaranteed response time, which is case of most avionics, can't be too complex, because you couldn't verify it does not have any slow worst cases.
So specifically for software engineering I'd say the current challenge is that the surrounding processes provide diminishing returns on reliability while ever increasing the barrier for innovation.

The key elements that differentiate flight system software from other less-specialized types of software are: Functional Safety, real-time, determinism, SOTIF (Safety of the Intended Function).  Derived from these are: functional safety architectures, concurrent programming, analysis and design methodologies, development methodologies, coding standards, testing methodologies, etc.
And the broad umbrella of "avionics software"  covers everything from boot-loaders, hypervisors, OS abstraction, Operating systems, drivers, middleware, System Services, and flight programs, User interfaces etc.  Each of which one could spend their entire career in.
Also, as one progresses up the software chain from, in some cases, tester, coder, developer, designer, architect, systems engineer, systems architect, functional safety manager, chief architect... the considerations change drastically.    A programmer follows a prescribed process, prescribed coding standards, prescribed testing methodologies etc, and may be unaware of the reasoning behind some of the design decisions being made by the architects and systems engineers.
As I see it, the area where innovation could make the biggest impact is in the approaches taken to satisfy functional safety and SOTIF.  This is largest cost driver as it leads to the need for certifying hardware and OS's, as well as a significant increase in the cost per line of code, costs for FMEA, FMEDA,  or program cost multipliers like triple redundant architectures with N-version programming.
I'd highly recommend a degree in Functional Safety.  This can take you far in not just aviation, but in automotive, industrial robotics, etc.
And the pay is not bad either!

Developing software for avionics is considered a specialized field with respect to requiring knowledge of embedded systems skills, handling communications protocols between avionics systems, and adhering to the appropriate industry standards. None of these things are particularly difficult, but the skills and knowledge are generally built up over a period of time in one's career.
Understanding embedded systems development is critical because, which a device might be using an operating system, some avionics hardware is programmed as a "bare machine." In this regard, you get no help from device drivers, file systems, or other OS-type services. On the other hand, there are likely code libraries that may be used to access certain parts of the embedded system, so you just need to understand the API.
Understanding inter-device communications is important because different devices exchange information using various types of protocols. The military in particular uses MIL-STD-1553 or ARINC 429 as standards. Some of these are translated into commercial equipment.
Finally, if you're developing software for the commercial industry, ALL software must adhere to and be compliant with the DO-178B standard. When the FAA certifies a piece of equipment, the testing is very comprehensive and includes reviews of the DO-178B certifications for the organization.


text:
Is it possible to have a separated boundary layer without having reversal flow?
To fix the ideas, let's consider an airfoil instead of a generic shape.
As far as I understand, the separation of the boundary layer takes place after there is a region of reversal flow on the suction side of the airfoil.
In the other hand, I can find that the separation point is different from the point of reversal flow.
For me, this raises a question if it is possible to have a separation point on the suction side of the airfoil without having any reversal flow point? in other words, is it possible for the boundary layer to separate be it laminar or turbulent without having first a region of reversal flow? or maybe is the flow reversal a necessary condition for the boundary layer to separate?
Could you please provide me a pointer?
Thank you

I think I have a partial answer that I have found in a paper [1]:
The following is a quote from the introduction:

It is too narrow a view to use vanishing surface shearing stress or
flow reversal as the criterion for separation. Only in steady
two-dimensional flow do these conditions usually accompany separation.
In unsteady two-dimensional flow the surface shear stress can change
sign with flow reversal without the occurrence of breakaway.
Conversely, the breakdown of the boundary-layer concept can occur
before any flow reversal is encountered.

[1]: Simpson, R. L. (1989). Turbulent boundary-layer separation. Annual Review of Fluid Mechanics, 21(1), 205-232.


text:
Approach clearance within a TAA
In a TAA with NOPT, control issues an approach clearance with an altitude restriction above the minimum altitude for the TAA. Control did not state straight-in, therefore are you required to preform the course reversal prior to executing the approach.

I am confused by what you mean by "control issues an approach clearance with an altitude restriction above the minimum altitude for the TAA." What was the exact wording used?

Did this happen to you?  What airport/approach?  Did you query ATC and ask for vectors for descent, or is this a hypothetical “what if”?  (And I don’t oppose what-if scenarios if they are plausible and learning can come from it…)

If a procedure entry is marked "NoPT" you should not perform the procedure turn. If it is not marked "NoPT" you should perform an appropriate course reversal.1 As far as I am aware, the vast majority of the time a procedure with a TAA will be marked "NoPT."
You will be cleared direct to either the left base, straight-in, or right base fix, and should perform a straight-in approach beginning at that fix. But see 5–4–5d7 for examples of modified TAAs which do not have one or both of the base areas; depending on the arrival course, a course reversal may be necessary.

I am confused about what you mean by "control issues an approach clearance with an altitude restriction above the minimum altitude for the TAA." It is possible that the minimum vectoring altitude is higher than the TAA minimum altitude, in which case—only if you are not already within the TAA—ATC should issue an instruction that sounds like:

Cleared direct CHARR, maintain at or above five thousand until entering the TAA, cleared RNAV Runway One-Eight Approach.2

But an approach clearance is an authorization to descend according to the published approach procedure all the way down to the DA/DH, so they should not be issuing a blanket altitude clearance in conjunction with an approach clearance.

1AIM 5–4–5d4
27110.65 4–8–1j


text:
What causes subtle cyclical changes in engine volume at cruise?
A few years back, while trying to snooze on a Jet2 flight up at cruising altitude, my semi-attention wandered to the droning of the engine. I realised there was a very subtle effect of its intensity rising and falling ever so slightly in a repeating fashion.  From memory, I'd say it was doing each rise and fall cycle over around 3-4 secs.  It was consistently regular in its pattern.  I've never heard that before but it was so subtle it could be it always does it and I've just never noticed.  I was intrigued as to what the mechanism might be.  Any thoughts?
I was in the window seat a row or two in front of the wing at the time if that's relevant to what's audible.
Thanks!

I suspect that what you are hearing is the interference pattern between the two engines.  The vibration combing from the rotation of one engine is some variable X hertz and the other engine is “X+/- a few” hertz.  This creates the interference pattern like you sometimes get with stereo speakers. On many prop and turbo-prop engines you have a prop-synchronizer that lets you make tiny RPM adjustments to find a  “sweet spot” where the interference pattern isn’t noticeable.

Also known as a beat frequency. https://en.wikipedia.org/wiki/Beat_(acoustics)

Many thanks for the answers!!

That is almost certainly a sound interference pattern due to a slight difference between the spool speeds of the two engines.  It’s a much more common problem on reciprocating or turbopropeller powered airplanes, where it can cause considerable discomfort for the passengers, but can also happen aboard turbofan powered aircraft, especially those with high bypass engines.

You said core speed, not fan speed.

I suppose better said as “spool speed”.

Well almost all the lower frequency non-white noise, which is what we are concerned with, is coming from the fan, so I would use that if I was writing it.

Many thanks for the answers!!


text:
Does cruise speed depends on rate of climb?
If an aircraft wants to fly at a fixed cruise speed, will the rate of climb have any effect on that? For example, let's assume an aircraft has to fly at a cruise speed of 0.8 Mach. How will the rate of climb be determined so that the aircraft can cruise at that altitude after gaining the altitude at which it is desired to cruise?

You're not really cruising unless your rate of climb is 0 ... I fail to see how cruise speed and rate of climb could have anything to do with eachother

Rate of climb and cruise speed are unrelated.
Once a climb is completed, and an aircraft levelled out, speed will be increased until the desired cruise speed is reached and then thrust adjusted to maintain that speed.

The only way that rate of climb and cruise are related is through the horsepower rating of the engine.  A more powerful engine will furnish the greater rate of climb and the higher cruising speed.
However, note that the horsepower requirement to maintain a given cruise scales as the third power of airspeed. So while adding ~20 horsepower to a 100HP engine will provide a significant improvement in rate of climb, the resulting increase in cruising speed will be small.

Does cruise speed depends on rate of climb?

Yes, cruise speed, rate of climb and altitude are related among each other due to the fact that both to fly horizontally and to gain altitude you need the power from the engine(s) and everything depends on the altitude.
In particular, on one side your airplane:

needs power to win the aerodynamic drag and the inertia in order to maintain or gain horizontal speed; aerodynamic drag depends on air density i.e. altitude;
it also needs power when climbing.

On the other side, the power supplied by the engine(s) must compensate for the sum of 1. and 2. and it depends on altitude and speed.
So for example if at a given altitude the whole power from the engine(s) is used to fly as fast as possible then there's no power left to climb and the rate of climb is simply zero. If at another condition the airplane is both flying fast and gaining altitude using again the whole power available, then there's no room to fly faster nor to climb faster; if a faster climb is needed in this condition, then the cruise speed must be reduced in order to trade a bit of power to gain altitude; and viceversa. Obviously if the airplane is flying at a certain speed without using the whole power available then it has room both to fly faster and/or gain altitude, anyway always within the limitation of the available power at that particular speed and altitude.


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What kind of qualifications would make me eligible to get a ramp operations job in Canada...?
What kind of qualifications would be required for me to be employed as a ramp agent in Canada..?

Welcome to Av.SE

Ramp jobs are generally entry-level, with no specific skills required. They can be fairly physical labor, loading & unloading luggage & cargo, pushing baggage carts, driving tugs, belt-loaders, & other vehicles in all weather & without enclosed cabs, so some amount of physical stamina is realistically required.
The ability to show up for work on time is a definite plus.
Don't know what background check and/or drug screen is required for these sorts of jobs in Canada; in the U.S. it isn't onerous & is typically paid for by the employer.
If you're asking about immigration & visa aspects, that's best addressed elsewhere.

thanks so much..I don't know if you have the answer to this question.. would I be eligible to be employed as an airport operations instructor in canada after moving from Kenya.. What are the requirements..? Thanks..

Sorry but that is immigration law, and I'm not qualified to discuss how that works for Canada. Not sure if there is a Stack where that would be on-topic or not.


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What is the difference between rate of roll and roll displacement?
I was studying Principles of Flight, I came across a sentence which is my question.
_ the aileron is known as a rate control since a given aileron angle of deflection determines a rate of roll, not a roll displacement.
My 1st question is what is the difference between rate of roll and roll displacement? What is roll displacement?
My 2nd question is, I know rate of roll is the rate at which an aircraft executes a turn expressed in degrees per second, can we say that rate of roll is the rate of change of heading as the aircraft rolls about its longitudinal axis?

Your "2nd question" conflates roll rate with turn rate; heading change is turn rate; bank angle change is roll rate.  In the case of an aileron roll, you could have a high roll rate with essentially zero heading change or turn rate; in a turn with a constant bank angle, you'd have zero roll rate with a constant turn rate.

Roll displacement is basically the bank angle of the aircraft. Rate of roll is the rate of change of bank angle per unit time: $\large \frac {∆bank \ angle}{∆time}$
A given aileron deflection does not result in a particular bank angle - it results in a particular rate of change of bank angle. In other words, holding the yoke at a particular deflection will not* result in the aircraft attaining a particular bank angle and staying there; instead, the aircraft will continuously roll at a constant roll rate for as long as the yoke is held at that angle.
*Ignoring any effects of lateral stability

(Also ignoring rotational inertia in the roll axis.  Good answer, but you might consider qualifying with "to a first approximation")

Good answer.  Per Ralph's comment on the question, I would recommend you take the opportunity to clarify the misunderstanding in the second question by briefly defining "turn rate"...


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Shockwave motion with angle of attack
why is the shockwave picking in itself off the aerofoil with increasing deflection of the leading edge?
Angle of attack:3degrees
Aerofoil: naca0018

What is the source of these images, please?

didn't you mean to write "increasing deflection of the trailing* edge"?


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Extrapolating Oswald Efficiency Factor from CL^2 vs CD Graph
I have plotted this CL^2 vs CD graph for a glide test performed in a flight simulator. I want to find the Oswald Efficiency Factor, e from it and I assume I can do that from its gradient. With a wing Aspect Ratio of 5.93, Equating the gradient (19.824) to 1/(eAR) and rearranging for e gives me a value of 0.00271 which is really strange as I was expecting it to be in the range 0.80-0.95. Also the gradient looks reasonable too. What am I doing wrong here?

You have the relationship between ${C_L}^2$ and $C_D$ the wrong way around. It is
$$
C_D = {C_D}_0 + \frac{{C_L}^2}{\pi\,e\,\Lambda}
$$
so the gradient should be
$$
\frac{1}{19.824} = 0.0504 = \frac{1}{\pi\,e\,\Lambda}
$$
which resolves to
$$
e = \frac{1}{\pi \cdot 0.0504 \cdot 5.93} = 1.064
$$
which is at least in the ballpark.
If you determine the slope $dC_D/d{C_L}^2$ the other way around you may find that it is slightly larger than $0.0504$ and will give you an efficiency factor in the $e = 0.9..0.95$ range.

-1 The efficiency factor cannot ever be greater than 1.  This is just as wrong or moreso as .00271.

If the slope is e.g. 0.052 instead of 0.0504, the Oswald factor will be slightly below 1.0, so in the correct range. But thanks for explaining the downvote.

Thanks a lot for this. Missed out on a simple manipulation. And yes, I did adjust the slope slightly and got the Oswald value as 0.97ish so it's reasonable.


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Trying to understand this pressure distribution over an aerofoil?
can someone please help me understand why the pressure is like that over the top and bottom surface of this aerofoil please?
Also, what do the arrows point out mean? Why are the front and end ones pointing in?

There are tons of answers about this topic. I personally suggest you to get some nice book about aerodynamics to lern the basics: making a lot of questions won't help you understand the basics rather will confuse you even more.

@sophit ever try to read a ton of books?  Sometimes, it's better to ask someone.

One very good book is enough and definitely better than many answers from random people on the internet. The questioner clearly lack the basics of aerodynamics, answering this question won't give it any help rather open a Pandora's box of other questions like: why does pressure decrease? Why and what is camber? Why symmetrical airfoil? What's stagnation point? Bernoulli? Why a pointy trailing edge? Turbolent flow? Why does airflow detach? What's momentum? ...

@Sophit (and others) Instead of sending new users away by telling them to read a ton of books first, why don't we invest in new users by helping them to get the right answer by asking the right questions? That way we foster a healthy community and a healthy stream of new questions. We write our own book here :-)

@DeltaLima: as said, the questioner clearly lack the basics of aerodynamics and, correct me if I'm wrong, this is not really the right website to obtain them i.e. this is not Wikipedia. Anyway I didn't send anybody away, just suggested to learn the basics and come back with maybe a more precise question

There are a few interesting aspects to these seemingly innocuous pressure diagrams that bear closer examination.
Firstly, this is a non symmetrical airfoil with a bit of camber.
This is why even the first diagram, at 0 degrees, it is generating more upward that downward force.  The difference is more apparent at 6 degrees Angle of Attack.

cambered wings can have zero lift at a negative angle of attack

The second item of note is the pressure gradients at the trailing edge.  Interestingly, these might be a result of insufficient airspeed, growing worse with increasing AoA.
Part of what makes wings work is the momentum, mv, of the airflow around the wing.  As speed increases, in the exact same manner turbulent flow separates from the transom of a boat, the airflow from the top and bottom of the wing is carried past the trailing edge before merging.
This is what would expect to see with a properly functioning airfoil.  The calm lower pressure stagnation zone directly behind the wing  would not be creating any buffeting on the trailing edge.

Thanks Robert, I read that the top is a suction region? Would it be correct to say this means the ambient pressure is lower than on the aerofoil surface then?

@FlightWatcher the arrows can be confusing.  Those pointing inwards are towards higher than ambient surface pressure.  Those pointing outwards from the surface point away from pressure lower than ambient.

The arrows represent the direction the pressures are acting.  Pointing towards the wing are increased pressures, and those pointing away are where the wing experiences a decreased pressure.  At the leading edge, you can conceptualize this as the point where the air collides with the wing and must be deflected away.  Meanwhile, due to fluid dynamics principles (e.g. Bernoulli's principle) the high-velocity air moving around the curved surface is related to a decrease in pressure at those locations.  In the diagrams, the leading and trailing edges are being pushed inward while the upper and lower surfaces are being pulled outward.  Summing up all the inward (increased) and outward (decreased) pressures, and looking at only the vertical component will result in a single upward force felt by the airplane.

Thanks fencerPTS


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Building Hours in a Foreign Country
I currently hold my Commercial Certificate with Instrument. Currently all FAA. Attended ATP Flight School in Texas. I was born in Nicaragua so I can legally work there. I was offered a job to work for a local airline called La Costeña. I would love to take that opportunity and fly in my home country but I’m confused on how this will all work. So I want to work towards my 1500hrs to eventually apply for Envoy then of course to AA through their flow through agreement. So here it is, I will be a First Officer. As far as logging my time, I see that Envoy requires 250hrs fixed wing PIC time and 100hrs of Cross country PIC within the 1500hr requirement. My question is, will I be able to log PIC time as a FO when I’m the sole manipulator of the controls? I know that legally speaking, according to the FAA, I could. But any idea on how Envoy views it? TIA

Hi, thank you for responding. Yes the aircraft does meet the requirements under 61.51(j)(2) since they fall under ICAO. I will be starting off on the Cessna Caravans and potentially later be trained on their ATR 42. Although the caravan is single pilot, they do have an agreement in place for FO’s to be able to log time as well. Not sure what they call this agreement in Nicaragua. Although I can log PIC time as an FO, do you know how some airlines view this? Do airlines look for or prefer Captain PIC time or does it matter much? Thanks again for the help.


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Is there a specification of how efficient a fuel consumption / fuel burn of an airplane or engine could be?
I'm working on a project to determine whether, based on real flight data, is a flight efficient in its fuel burn/consumption. From the analysis of the flight data, i got fuel burn calculation, per phase and overall.
I want to know if there's a specification on the numbers that would help me in determining the efficiency of a flight that i can compare to, based on the fuel burn calculation of the aircraft engine from a flight, like official numbers from the manufacturer or someone similar that is reliable


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Can single engine/smaller aircraft turn off ADS-B?
I was just looking at the adsbexchange website, and was wondering if it was possible for smaller, private aircraft to turn off their ADS-B? I was wondering this because id figure that maybe not everyone wants to have their live flight info publicly available online, especially if its a smaller flight.
I know its illegal to do but in theory is it possible on smaller aircraft in general? And if so, would the only way to track them if they turned off their ADS-B and their Transponder be to use radar?
I'm not a pilot so I may not be too well versed on this subject so thank you.

Welcome to aviation.SE! You said you know it isn't allowed, so I assume you aren't asking about regulations. Are you asking about physically turning it off? If so, this question might have some useful information.

In the US it's only illegal in certain types of airspace. In most of the US you don't even need to have a transponder, or in fact even an electrical system in a plane.

@Pondlife Hi, Yes I am talking about physically turning it off.

@TomMcW In the US, if you have a transponder or ADSB installed, you are required to operate them at all times, even in airspace where you’re not required to have it in the first place.

@StephenS I was unaware of that.

@TomMcW See 91.215(c) and 91.225(f)

Yes, it is very possible. As you say, it may be against the rules, but it is possible. ADS-B Out may be integrated in a "standard" 4096-code Mode A/C transponder (which can be disabled), or it may be wired in to another system on the aircraft, such as the anti-collision strobe (which can also be disabled). A standalone ADS-B device may even be plugged into a 12V accessory outlet, though I believe that's more common for an ADS-B In setup (where various data, most importantly nearby traffic, is fed in to a display device)—I'm not sure if that counts as a valid Out setup.
In any case, as the answers at the linked question describe, every electrical device on an aircraft should have the capability to be powered off. In an emergency, especially a fire onboard, the immediate safety of the aircraft and its occupants is prioritized above the generally enhanced safety situation afforded by ADS-B.
But there are other reasons you may not see an aircraft on a flight-tracking website:

Pilots can make a request, both with the FAA and with the website, to have their aircraft hidden. This is very common. However, this will not be the reason you do not see an aircraft on ADS-B Exchange; they are very clear that they do not filter or block any aircraft from their data.
The website may not have any data feeds nearby. Official ATC displays use ADS-B receiver antennas that are installed and maintained by the government or other appropriate organization; third-party sites may have an arrangement to access some of this data, but if not they must rely on a network of volunteers with privately-owned receivers. There may not be any such volunteers within range of the aircraft.

In particular, in the United States, many ADS-B transponders broadcast on a frequency of 1090 MHz, the same as in the rest of the world. But smaller aircraft that will not operate above 18,000' MSL nor outside of the United States may use a cheaper "Universal Access Transceiver" which broadcasts on 978 MHz. Fewer aircraft use this technology which means fewer volunteer receivers are set up for it; if your aircraft of interest has an ADS-B Out device that uses 978 instead of 1090, it is less likely to appear on third-party sites.

The aircraft may not have ADS-B Out installed at all, and that may be quite legal. In the United States, 14 CFR 91.225 lists the airspace where ADS-B Out is required, and it is not "all airspace" by any means (though it does include the airspace in and above busier airports, as well as all airspace above 10,000' MSL that is at least 2,500' above the ground).

And yes, if the the aircraft's ADS-B is turned off the only way to track them would be by using their transponder (secondary radar) or listening for an echo bouncing off the physical aircraft (primary radar). And if the pilot turned off the transponder as well, primary radar would be the only automated means of tracking the aircraft. This would still be quite possible, as long as the aircraft was high enough; one of the benefits of ADS-B is that the cheaper receiver sites allow for greatly increased low-altitude coverage, which the expensive primary radar antennas do not always provide (see: Can someone actually "fly under the radar"?).
Note that even in non-radar airspace known aircraft can be "tracked" if the pilot reports over a known location at a known time, and ideally provides an estimate of when they will be over the next location.

There are no ADSB-Out devices that plug in to your accessory outlet. They all have to be permanently mounted and comply with FAA regs. https://www.faa.gov/documentLibrary/media/Advisory_Circular/AC_20-165B.pdf

@JScarry There actually are ADS-B Out devices that plug in to your accessory outlet. The FAA isn't the only aviation regulation body in the world, and there are countries where portable units do meet local regulations.

@HiddenWindshield A popular example being the "SkyEcho" which is a portable device for use in the UK

@HiddenWindshield Good to know.


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Is company-sponsored training considered compensation?
I have a company looking to hire me to help setup their new flight department. During that process and while I am on salary they want to pay for me to get the rest of my ratings. I don't believe this crosses any lines, but wanted your thoughts.
I am in the US so I’m concerned with the FAA. I’m particularly concerned with the FAA and IRS having issues with someone else paying for my flight training. I am concerned they may see it as some form of compensation for someone who doesn’t have a commercial license.


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Can anyone help identify this turbine blade?
At the local army/navy surplus store and found this in a "junk" box. Got it for $1. Would live to know what airframe this came off of. Im new to this so compressor blade? Compressor turbine?
Markings:
Written in sharpie 8740
Engraved 8740 (Hand engraved on bottom)
Stamped 6205DJ92
Thanks

Unlikely 8740 steel low alloy. That could only be used in the temperatures on the first few stages of the compressor inlet.

Maybe not an aircraft engine at all. Gas turbines are used in many places other than aircraft. The Abrams M1 tank used a gas turbine. Many military ships use them for extra power. The plant that generates electricity for your home uses steam turbines.

Good call on the abrams. Was also thinking perhaps due to the overall LACK of markings, inspections stamps etc that perhaps this is an APU. Ill expand my search. Thanks!


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Why in aviaton they are using Electro Mechanical Actuators instead of Electric Linear Motors?
In my opinion they are much more compact, the design may be needed to change in order to still be a fail-safe component, also, may be need to account for jamming and load disconnection safety devices, but the fact that there are less moving parts make it more reliable, lighter and simpler. Why they are not even evalued for the actuation of the flight controls, brakes, nose and landing gear retraction?
Here the links of the images for reference:
Linear electric motor: https://www.google.com/search?client=firefox-b-m&biw=867&bih=448&tbm=isch&sa=1&q=linear+electric+motor&oq=linear+electric+motor&aqs=mobile-gws-lite..0l5#imgrc=YR8Gpr1CzS8W1M
EMA: https://www.google.com/search?q=electro+mechanical+linear+actuator&client=firefox-b-m&source=lnms&tbm=isch&sa=X&ved=0ahUKEwj4k_COj6yAAxUYR_EDHQLVAkMQ_AUIBigB&biw=867&bih=448#imgrc=c0Ez4IYa6_csTM

Linear motors are generally fast and precise, but provide low forces relative to jack screws or hydraulics.

For brakes and control surfaces, i.e ones that moves swiftly, it's more about space and power: electric actuators is not powerful enough within the space limit so hydraulics is preferred instead, but it's slowly transitioning to electrics just like on cars. Most small and medium size cars uses electric power-steering. Electric brake calipers on cars has been designed and demoed a decade ago but is not used on production cars yet.
For other slow-moving parts, elevator trim and flaps, motor+screw is simply the lightest, most efficient and also cheapest solution. The screw mechanism has a huge reduction gear ratio so you only need a small motor to generate a large force, although a bit (very) slow. Also, since those parts needs to hold at a specific position for a long time, and the auto-locking property of the screw mechanism means you can hold without using any energy, any additional mechanism, and no heat is generated as well.
Using linear electric motor on landing gears is actually a neat idea. This is one of those places that motor+screw is a bit too slow while hydraulics is a overkill, and space is plenty.

Yes, Thanks for your feedback. I expect that electric linear motors or even magnetic actuators will be used starting first from small electric planes(new evtols) and than later on larger planes.


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Would shockwave over a Supercritical aerofoil move downstream with Angle of attack?
over a supercritical aerofoil, would a shockwave move downstream with increase in angle of attack?
I thought yes as the top surface is flat?

Haven't you already asked the same question some days ago?

Hi, so that question is concerning deflection, this one is concerning a supercritical aerofoil with angle of attack

I do not think there is a single answer for all supercritical airfoils -- and the answer will also vary with Mach (and probably Reynolds number).
Some supercritical airfoils are designed to be shock-free.  Are you operating one of those airfoils above the design mach number?
Generally speaking, increasing lift will increase acceleration at the suction peak (around the LE and front of the airfoil).  The region of supersonic flow on the front, upper surface of the airfoil will grow -- the highest Mach number in that supersonic region will increase.
In general, I believe that will cause the shock to move forward and increase in strength.

And I believe that will cause the shock to move backwards and increase in strength. A stronger shock means a larger change in speed and pressure, and that higher pressure is reached in the outer flow only further downstream. In other words, the air "does not see" a need to drastically change its parameters until further downstream.

Hi Rob and Peter, sorry just to clarify, does that ‘forward’ mean towards the leading edge? Also why does increase in AOA increase the maximum Mach over the aerofoil? Wouldn’t increasing the aoa make it harder for the flow to travel over the aerofoil?

@PeterKämpf may be right (that I have my conclusion backwards).  Without taking a stand on that (I'll have to do more work to be sure) -- Increasing AoA always causes more acceleration over the leading edge and a higher suction peak.  The higher velocity is fundamentally how more lift is achieved.  And yes, 'forward' means towards the leading edge.


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Confused about screen height definition
I’m a bit confused about screen height definition and I’m seeking help to understand it. I understand that this height for landings is at least 50 ft above the landing threshold for all airplane categories. For takeoff is at least 50 ft or more for Normal and Utility categories and at least 35 ft or more for the Transport category. My question is: For takeoffs is this screen height measured above the departure end of the runway (or above the end of the clearway if any) or it’s measured when a Piper for example is 50 ft above the runway after taking off?
If it’s measured above the DER, does that mean that the actual takeoff DISTANCE of a runway with no clearway will be the entire runway length always? Since the definition of Takeoff Distance is the distance from the Brake Release Point to when the plane crosses the screen height?
Thank you!

For takeoffs is this screen height measured above the departure end of the runway (or above the end of the clearway if any)

For the takeoff distance available calculation, yes this is correct

or it’s measured when a Piper for example is 50 ft above the runway after taking off?

This is correct for the takeoff distance required calculation.

If it’s measured above the DER, does that mean that the actual takeoff DISTANCE of a runway with no clearway will be the entire runway length always?

Yes, this is known as the "balanced field length", when TODA = TORA = ASDA

This post is 5mo old so maybe something has changed but IFR departure procedure is 35ft over the departure end of runway for Cat A aircraft (Pipers). This 35ft is measured for the usable runway length for takeoff. The answer above is correct but just know 35ft is your magic number in the US. It may be 50ft in other countries not sure though.


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Manifold Pressure System

Hi to all. I read about how MAP works and have a question. Do constant speed planes like the c182 or pa44 have an additional Venturi (apart from the one in the carburetor) in the induction system past the throttle plate?
Thanks!

No. It's just a tap-in to the intake passage on the downstream side of the carb. It's just measuring the absolute pressure in the duct, which is always less than atmospheric in the absence of turbocharging or supercharging. Really, it's literally just a barometer, and is graduated as one. You can take a MP gauge and use it as a barometer at home.
RPM changes with a CS prop cause a small manifold pressure change due to the change in pumping rate of the piston with RPM and thus the velocity of the intake stream. A drop in RPM from a change in governor setting causes a small manifold pressure rise as the flow rate drops, and vice versa.
You anticipate this when making RPM reductions, where you are normally making the throttle change first. For example if reducing power from 24" and 2400 RPM to 22" and 2200 RPM, I might throttle back to 21.5", anticipating it will pick up half an inch of MP when I reduce the prop RPM to 2200.